Recent advances in ceramic superconductor technology have made a wide variety of superconductor applications technically possible and economically feasible. This is because, as is well-known, ceramic superconductors have relatively high superconducting transition temperatures (T.sub.c), as compared to previously known superconductors, e.g., niobium-based superconductors. As a consequence of the high T.sub.c of modern ceramic superconductors, relatively expensive and difficult to handle coolants such as liquid helium, which had been required to cool previously known superconductors to about four (4) Kelvins in order to achieve superconductivity, are not required to cool modern ceramic superconductors. Instead, modern ceramic superconductors can be cooled to their superconducting state with relatively inexpensive and easy to handle coolants, e.g., liquid nitrogen.
One obvious application of high-T.sub.c superconductors is the transmission of electricity. Not surprisingly, several methods have been developed for forming ceramic superconductors into electrical transmission wires. Unfortunately, ceramic superconductors tend to be brittle and easily broken, while electrical wires must typically be flexible and relatively impervious to breaking under ordinary operating conditions. Accordingly, methods for coating a flexible metallic wire substrate with a ceramic superconductor layer have been disclosed, e.g. the process disclosed in copending U.S. patent application Ser. No. 265,827, entitled "Substrate for a Ceramic Superconductor", assigned to the same assignee as the present invention.
While supporting a ceramic superconductor layer on a substrate can help alleviate the brittleness problem noted above, at least to some extent, where the substrate is a flexible wire other technical complications can arise. For example, material from the wire substrate can diffuse into the ceramic crystal structure and dope the crystal structure. This doping of the ceramic crystal structure can limit the amount of current the superconductor layer can carry in the superconducting state. Accordingly, processes such as the method disclosed in co-pending U.S. patent application Ser. No. 528,707, entitled "Method for Electroplating of Yttrium Metal in Nonaqueous Solutions", have been introduced which disclose methods for forming a diffusion barrier between the substrate and superconductor. Additionally, the ceramic superconductor must be protected from water and other contaminates that could potentially damage the ceramic or destroy the ceramic's superconducting properties. Thus, it is desirable that the superconductor wire be coated with a material which will have minimal chemical interaction with the ceramic material, but which will provide a protective cover with low electrical contact resistance for the ceramic material. A method for coating a ceramic with a protective layer is disclosed in a co-pending U.S. patent application entitled "Anhydrous Electrophoretic Silver Coating Technique", assigned to the same assignee as the present invention. Finally, ancillary steps in the superconductor wire manufacturing process may be desirable. For example, it may be desirable to magnetically align the grains of the superconductor ceramic layer, in order to maximize the current carrying capacity of the wire in its superconductive state. Additionally, it may be desirable to provide a diffusion inhibiting barrier to prevent the protective cover from diffusing into exterior components during heating. Such a barrier is disclosed in a co-pending U.S. patent application entitled " Diffusion Bonding Inhibitor for Silver Coated Superconductor", assigned to the same assignee as the present invention.
In light of the above discussion, it will be appreciated that the manufacture of industrially useful ceramic superconductor wire can involve several steps. In the case of a manufacturing process which is designed to mass produce lengths of superconductor wire, the steps discussed above are preferably accomplished in an integrated, automated sequence, after which the manufactured superconductor wire can be wound onto a spool or other industrially appropriate configuration. The present invention recognizes that a ceramic superconductor wire can be produced by a single apparatus using a continuous, integrated process to fulfill each of the manufacturing considerations noted above.
Accordingly, it is an object of the present invention to provide a method and apparatus for manufacturing a ceramic superconductor wire which produces an effectively flexible superconductor wire. It is another object of the present invention to provide a method and apparatus for manufacturing a ceramic superconductor wire with a protective coating. A further object of the present invention is to provide a method and apparatus for manufacturing a ceramic superconductor wire in which the grains of the ceramic superconductor are substantially aligned. Another object of the present invention is to provide a method and apparatus for manufacturing a ceramic superconductor wire in which a diffusion barrier is established between the wire substrate and the ceramic superconductor layer. Yet another object of the present invention is to provide a method and apparatus for manufacturing a ceramic superconductor wire which produces a superconductor wire in an integrated, continuous process. Finally, it is an object of the present invention to provide a method and apparatus for manufacturing a ceramic superconductor wire which is comparatively cost effective.